I think i have the idea who are the culprit .
As There has been a new promo of Rakht Samband in Imagine that in 2nd August there will be the disclosure of the bad past of Sadhya's husband .I think Yuvraaj is impotent ; his family to save his son and family's reputation arrange the marriage of Sandhya with yuvraaj . As she is blind she may not see with whom she is having the physical relationship . Niraj is brought to make physical relationship with Sandhya and make her pregnant and the family will say this child is Yuvraj's. So when they arrange the marriage with Sandhya his father did't know about the truth of yuvraaj , but in the marriage ceremony i guess he got to know about it , so Yuvraaj 's family killed him and hang him .
What you all think the reason of the murder or who had killed him , Please write here.